Dilated cardiomyopathy (DCM) is the most common type of cardiomyopathy, affecting as many as 1 in every 250 individuals, and represents a significant public health concern due to its high mortality and morbidity rates. The disease, characterized by systolic dysfunction and left ventricular dilation, is a leading cause of heart failure and a prevalent indication for heart transplant. The pathophysiology of DCM has remained elusive because of the heterogeneity of the disease, in which numerous mutations to cytoskeletal proteins, e.g. vinculin, VCL, and sarcomeric proteins, e.g. ?-tropomyosin, TPM1, have been implicated; these diversities are compounded by the fact that cardiomyocytes (CMs) from adult hearts are difficult to isolate and culture, making in vitro analysis difficult. With th huge burden DCM creates for affected families and society, there is a significant need to develop accurate disease models that unravel complex pathophysiology and enable the development of effective treatments. To address this need, we propose to develop an in vitro model of DCM using CMs generated from patient-derived human induced pluripotent stem cells (hiPSCs) and investigate the cellular pathology associated with the disease. hiPSC-CMs used in these studies originate from a family cohort carrying mutations in VCL and TPM1, where multiple family members heterozygous for both mutations have been diagnosed with DCM. In Aim 1, we will generate CMs from the patient-derived hiPSCs and familial controls. Additionally, we will create isogenic lines using genome engineering to mutate the loci of interest in familial control lines and to repair mutations in patient lines. Patient hiPSC-CMs will be assessed for structural abnormalities, such as sarcomere or intercalated disc disorganization, and compared to familial and isogenic controls. In Aim 2, we will utilize functional analyses - i.e. calcium imaging, voltage imaging, traction force microscopy, multielectrode array recording - to characterize the electro-mechanical coupling in patient and control hiPSC-CMs. The assays will determine any functional aberrations resulting from VCL/TPM1 mutations within the familial and isogenic lines. Results from these studies will create a better understanding of the role of VCL/TPM1 mutations in the development of structural and functional abnormalities that may combine to cause DCM in patients, and potentially provide insight into future therapeutics.